Mask health monitor using a faraday probe

ABSTRACT

In an ion implanter, an ion current measurement device is disposed behind a mask co-planarly with respect to a surface of a target substrate as if said target substrate was positioned on a platen. The ion current measurement device is translated across the ion beam. The current of the ion beam directed through a plurality of apertures of the mask is measured using the ion current measurement device. In this manner, the position of the mask with respect to the ion beam as well as the condition of the mask may be determined based on the ion current profile measured by the ion current measurement device.

RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 12/845,665, filed Jul. 28, 2010 now U.S. Pat. No.8,164,068, which claims priority to U.S. Provisional Patent ApplicationSer. No. 61/229,852, filed Jul. 30, 2009, both of which are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to the field of device fabrication.More particularly, the present disclosure relates to ion implantationthrough a mask and a device and system to monitor the health of the maskused during ion implantation.

2. Discussion of Related Art

Ion implantation is a standard technique for introducingconductivity-altering impurities into substrates. A precise dopingprofile in a substrate and associated thin film structure is criticalfor proper device performance. Generally, a desired impurity material isionized in an ion source, the ions are accelerated to form an ion beamof prescribed energy, and the ion beam is directed at the surface of thesubstrate. The energetic ions in the beam penetrate into the bulk of thesubstrate material and are embedded into the crystalline lattice of thesubstrate material to form a region of desired conductivity.

Such an ion implanter may be used to implant desired dopants into asilicon substrate to form solar cells. These solar cells providepollution-free, equal-access energy using a recurring natural resource.Due to environmental concerns and rising energy costs, solar cells arebecoming more globally important. Any reduced cost to the manufacture orincreases in production of high-performance solar cells or anyefficiency improvement to high-performance solar cells would have apositive impact on the implementation of solar cells worldwide. Thiswill enable the wider availability of this clean energy technology.

Solar cells may require doping to improve efficiency. FIG. 1 is across-sectional view of a selective emitter solar cell. It may increaseefficiency to dope the emitter 200 and provide additional dopant to theregions 201 under the contacts 202. More heavily doping the regions 201improves conductivity and having less doping between the contacts 202improves charge collection. The contacts 202 may only be spacedapproximately 2-3 mm apart. The regions 201 may only be approximately100-300 μm across.

FIG. 2 is a cross-sectional view of an interdigitated back contact (IBC)solar cell. In the IBC solar cell, the junction is on the back of thesolar cell. The doping pattern is alternating p-type and n-type dopantregions in this particular embodiment. The p+ emitter 203 and the n+back surface field 204 may be doped. This doping may enable the junctionin the IBC solar cell to function or have increased efficiency.

In the past, solar cells have been doped using a dopant-containing glassor a paste that is heated to diffuse dopants into the solar cell. Thisdoes not allow precise doping of the various regions of the solar celland, if voids, air bubbles, or contaminants are present, non-uniformdoping may occur. Solar cells could benefit from ion implantationbecause ion implantation allows precise doping of the solar cell. Ionimplantation of solar cells, however, may require a certain pattern ofdopants or that only certain regions of the solar cell substrate areimplanted with ions. Previously, implantation of only certain regions ofa substrate has been accomplished using photoresist and ionimplantation. Use of photoresist, however, would add an extra cost tosolar cell production because extra process steps are involved. Otherhard masks on the solar cell surface likewise are expensive and requireextra steps. Accordingly, there is a need in the art for an improvedmethod of implanting through a mask and, more particularly, a healthmonitor for a mask used for ion implantation.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention are directed to anapparatus and method of determining alignment of a mask in an ionimplanter. In an exemplary method, an ion beam is directed through aplurality of apertures of a mask toward a platen configured to support atarget substrate. An ion current measurement device is disposed behindthe mask a substantially co-planar relationship with respect to thetarget substrate as if the substrate is positioned on said platen. Theion current measurement device is translated across the ion beam. Theposition of the ion current measurement device is recorded as ittranslates across the ion beam. A current of the ion beam directedthrough the plurality of apertures of the mask is measured using the ioncurrent measurement device at the recorded positions. A current signalis generated in response to the measured ion beam current from the ioncurrent measurement device at each of the recorded positions. Thecurrent signal is transmitted to a controller and a control signal isgenerated by the controller and is used to position at least one of theion beam or the mask based on the control signal such that a mean ionbeam angle is centered with respect to a center one of the plurality ofapertures of the mask.

In an exemplary embodiment, an ion implanter system includes an ionsource, a beam line assembly, a mask, an ion current measurement deviceand a controller. The beam line assembly is configured to extract ionsfrom the ion source to form an ion beam and direct the ion beam toward aa platen. The mask is disposed in front of the platen. The mask has aplurality of apertures to allow respective portions of the ion beamthrough the mask toward a said platen. The ion current measurementdevice is disposed substantially co-planarly with the surface of thetarget substrate as if the target substrate was positioned on theplaten. The ion current measurement device is configured to translateacross the ion beam co-planarly with respect to the surface of thetarget substrate. The ion current measurement device is also configuredto generate signals proportional to the ion current received through theapertures as the measurement device translates across the ion beam. Thecontroller is configured to receive the signals from the ion currentmeasurement device and determine an orientation of the mask with respectto the target substrate such that angles of the ion beam through one ormore of the plurality of apertures in the mask are aligned.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a selective emitter solar cell;

FIG. 2 is a cross-sectional view of an interdigitated back contact solarcell;

FIG. 3A is a block diagram of a representative ion implanter inaccordance with an embodiment of the present disclosure;

FIG. 3B is a cross-sectional view of implantation through a mask;

FIG. 4 is a front schematic view of implantation through a mask using aFaraday probe in accordance with an embodiment of the presentdisclosure;

FIG. 5A is a schematic perspective view of implantation through a maskusing a Faraday probe in accordance with an embodiment of the presentdisclosure.

FIG. 5B is a top cross-sectional schematic view of implantation througha mask using a Faraday probe in accordance with an embodiment of thepresent disclosure;

FIG. 6 is a first top cross-sectional view of mask-ion beam angularalignment in accordance with an embodiment of the present disclosure;

FIG. 7 is a second top cross-sectional view of mask-ion beam angularalignment in accordance with an embodiment of the present disclosure;

FIG. 8 is a first top cross-sectional view of mask-substrate alignmentin accordance with an embodiment of the present disclosure;

FIG. 9 is a second top cross-sectional view of mask-substrate alignmentin accordance with an embodiment of the present disclosure;

FIG. 9A illustrates a feature profile associated with a large gapbetween a mask and a substrate or platen.

FIG. 9B illustrates a signal profile for a mask having worn aperturesoverlayed on a signal profile for a mask having non-worn apertures.

FIG. 10 is a front perspective view of an embodiment of a Faraday probeto test for mask erosion in accordance with an embodiment of the presentdisclosure; and

FIGS. 11-13 are front perspective views of the embodiment of a Faradayprobe to test for mask erosion of

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention, however, may be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

FIG. 3A is a block diagram of an ion implanter 115 including an ionsource chamber 120. A power supply 121 supplies the required energy tosource chamber 120 which is configured to generate ions of a particularspecies. The generated ions are extracted from the source through aseries of electrodes 114 and formed into a beam 103 which passes througha mass analyzer magnet 116. The mass analyzer is configured with aparticular magnetic field such that only the ions with a desiredmass-to-charge ratio are able to travel through the analyzer for maximumtransmission through the mass resolving slit 117. Ions of the desiredspecies pass from mass slit 117 through deceleration stage 118 tocorrector magnet 119. Corrector magnet 119 is energized to deflect ionbeamlets in accordance with the strength and direction of the appliedmagnetic field to provide a ribbon beam targeted toward a work piece orsubstrate positioned on support (e.g. platen) 102. In some embodiments,a second deceleration stage 122 may be disposed between corrector magnet119 and support 102. The ions lose energy when they collide withelectrons and nuclei in the substrate and come to rest at a desireddepth within the substrate based on the acceleration energy. A mask 104and ion current measurement device 106 (shown in FIG. 4) are disposedproximate a process chamber which houses platen 102.

FIG. 3B is an exploded cross-sectional view of implantation of asubstrate 100 utilizing a mask. When a specific pattern of ionimplantation in a substrate 100 is desired, a mask 104 may be placed infront of substrate 100 in the path of an ion beam 103. This mask 104 maybe a shadow or proximity mask. The substrate 100 may be, for example, asolar cell which is placed on platen 102, which may use electrostatic orphysical force to retain the substrate 100 thereon. The mask 104 hasapertures 105 that correspond to the desired pattern of ion implantationin the surface of substrate 100.

Use of the mask 104 eliminates process steps, such as silkscreening orlithography, required for other ion implantation techniques. However, itmay be difficult to properly place the mask 104 relative to thesubstrate 100 to allow the desired pattern of ion implantation. The mask104, the ion beam 103, and the platen 102 all have linear and angulartolerance variations that may lead to misalignment or misplacement ofthe mask 104.

FIG. 4 is a front schematic, view of implantation assembly including amask using a Faraday probe positioned parallel or co-planarly withsubstrate 100 as if the substrate was positioned on the platen 102 inthe exemplary ion implanter shown in FIG. 3A. The mask 104 includes aplurality of apertures 105 and is disposed in front of the substrate 100(partially outlined with dotted lines behind the mask 104). Theapertures 105 may also be configured as holes, slots or other geometryconfigured to allow portions of the ion beam through the mask. The mask104 may be translated or positioned in multiple axes using a translationmechanism 108. This translation mechanism 108 may be a servo motor usedto variably position the mask linearly with respect to a distance fromsubstrate 100 and angularly with respect to the transmission of ion beamin the z direction through the apertures. The substrate 100 may bescanned behind the mask 104 in one embodiment to obtain a uniformpattern of implanted regions. The implanted regions may resemble“stripes” across the surface of the substrate 100 in the X and Ydirections. For proper operation, the mask 104 must be aligned (asdescribed below) with substrate 100 as well as the ion beam implantedthrough the apertures 105. Over time, the mask 104 may erode and theapertures 105 may become incorrectly sized or have incorrect dimensions,thereby compromising a desired implant profile.

The Faraday probe 106 is disposed behind mask 104 and is configured tomove in the X direction across the ion beam 103 when the substrate 100is not positioned on platen 102. The Faraday probe is position on thesame plane (i.e. the Z direction) as the surface 100 a of substrate 100as of the substrate was positioned on platen 102. The Faraday probe 106,or Faraday cup, is used to measure the current of ion beam 103 incidenton the same plane as surface 100 a to mimic implantation of regions ofsubstrate 100 aligned with apertures 105 of mask 104 as if the substrate100 was positioned on the platen 102. Alternatively, multiple Faradaycups may be included on Faraday probe 106 or multiple Faraday probes 106may also be employed. The Faraday probe 106 is positioned behind themask 104 and coplanar with a surface 100 a of substrate 100 in place ofsubstrate 100 to mimic implantation of the ion beam in the substrate.Faraday probe 106 is configured to move in the X direction viatranslation mechanism 107, which may be, for example, one or more servomotors. Faraday probe 106 is connected to a current measurement device109. In this manner, the Faraday probe 106 receives the current of theincident ion beam 103 as if it were substrate 100 and measurement device109 measures the current that travels from the Faraday probe 106 toground. This current is converted to a control signal which is suppliedto controller 110.

The controller 110 reads the control signal from the current measurementdevice 109 and determines if position correction is necessary for themask 104 or ion beam 103. The controller 110 can send signals to thetranslation mechanism 108, the translation mechanism 107, or anothersystem or component to correct positioning of the mask or to translatethe Faraday probe. In one embodiment, a separate motion control systemmay be used to process the new desired positioning requirements and todrive the various mechanisms, systems, and components. The controller110 also may adjust the ion beam or substrate 100. Use of the Faradayprobe 106 enables more accurate placement of the mask 104, substrate100, and ion beam and improves implantation of the substrate 100 byoptimally aligning the apertures 105 of mask 104 with the substrate 100when the substrate is positioned on platen 102.

FIG. 5A is a schematic perspective view of ion beam 103 portions ofwhich travel through the apertures of mask 104. As can be seen, the mask104 is orthogonal to the direction of travel of the ion beam 103 (i.e. Zdirection). As the ion beam 103 travels through the apertures of mask104, portions of the ion beam 103 ₁ . . . 103 _(N) would form “stripes”of dopant implantation across the surface of the substrate when thesubstrate is positioned on the platen. The other portions of the ionbeam 103 incident are blocked by the area of the mask between theapertures. Faraday probe 106 is positioned behind mask 104 andtranslates in the X direction across the ion beam portions 103 ₁ . . .103 _(N). Faraday probe 106 is illustrated as being positioned towardthe top (in the Y direction) of ion beam 103. However, this is forexplanatory purposes and the probe 106 may be positioned anywhere alongthe Y axis of the ion beam 103. However, it is optimal that the Faradayprobe 106 be parallel or substantially co-planar with the surface 100 a(shown in FIG. 4) in the z direction so that the probe receivessubstantially the same ion beam portions 103 ₁ . . . 103 _(N) that wouldbe received by the substrate 100 as if the substrate was receivingimplantation of the ion beam 103 as the probe translates across the beam103 in the X direction. In this manner, the ion current of the portionsof the beam that travel through the apertures is measured by the Faradayprobe. In addition, the position of the probe 106 is monitored such thatvariations in ion beam current detected by the probe may be correlatedwith a particular one or more of the plurality apertures in mask 104.For example, over time the edges of the apertures of the mask 104 mayerode from constant exposure to beam 103. This may cause the width ofone or more apertures to enlarge beyond a given implant and alignmenttolerance level. By monitoring the position of the probe as ittranslates across the ion beam portions 103 ₁ . . . 103 _(N), the ionbeam current measured at a particular one of the apertures may bedetermined to be outside a given tolerance level. Accordingly, thecondition of the mask 104 and more particularly the condition of theapertures of the mask may be monitored. It has been found that anincrease in the width of an aperture 105 of up to about 20% can betolerated without compromising the integrity of an implant profile for asolar cell. This is due to the fact that a masked area (i.e. the area ofthe substrate not disposed behind one of the apertures 105) is typicallymore heavily doped than the portions of the substrate behind theapertures 105 of an emitter cell which are more lightly doped. As theedges of an aperture 105 erode, the emitter area becomes more heavilydoped than designed. This may compromise solar cell performance.

FIG. 5B is a top cross-sectional view of the ion beam shown in FIG. 5Athrough mask 104 and the positioning of the Faraday probe 106 withrespect to the mask and a substrate 100 as if the substrate was present.As mentioned above, the Faraday probe 106 translates in the X directionbehind mask 104 as indicated by the arrow 111. As the Faraday probe 106translates behind the mask 104, a signal is generated proportional tothe exposed current of the ion beam 103. This current and the knownposition of the Faraday probe 106 monitor the health or condition ofmask 104. The Faraday probe 106 can, for example, be used to properlyposition the mask 104, optimize the spacing in the Z direction betweenthe mask 104 and the substrate 100, monitor the mask 104 for excessivewear or erosion, monitor the mask 104 for fracturing, or monitor themask 104 for thermal control.

The signal generated by the probe 106, which is proportional to the ionbeam current incident on the probe as it translates across the beam inthe X direction indicated by arrow 111, also provides alignmentinformation with respect to the ion beam 103 and mask 104. Inparticular, if the mask 104 is aligned with the beam such that theangles of the ion beam 103 emanating from the apertures 105 of the mask104 cause the beam portions 103 ₁ . . . 103 _(N) (shown in FIG. 5A) tofall within the desired implant region; then the probe 106 may detect adesired ion beam current range indicating that the mask 104 is alignedwith the divergent angles of beam 103. Because the beam 103 is composedof like-charged molecules, the beam 103 will naturally diverge causingdivergent beam angles. If however, the probe 106 measures ion beamcurrent emanating from a particular one or more of the apertures 105that is not within the desired range, this indicates that the mask 104and beam 103 are not aligned or at least not optimally aligned tosatisfy implant region requirements for an intended substrate 100.

FIG. 6 is a first top cross-sectional view of mask-ion beam angularalignment. The Faraday probe 106 may be used for alignment between themask 104 and the ion beam 103. The mask 104 can be oriented with respectto the ion beam 103 so that the beam angles generated by the apertures105 will implant the proper regions of an intended substrate 100.Additionally, by aligning the mask 104 with respect to the existing beamdivergence angles of the ion beam 103, the mask 104 can optimize theavailable current of the ion beam 103. The angle of the ion beam 103that passes through the apertures 105 is fixed, and, thus, the amplitudeof the ion beam 103 measured by the Faraday probe 106 is optimal whenthe angle of the ion beam 103 and angle of the mask 104 are aligned. Inother words, since the admittance angles through the apertures 105 ofmask 104 are fixed (i.e. the apertures are positioned through particularlocations across the mask) the ion beam current measured by the probe106 as it translates across the beam in the X direction is optimal whenthe beam divergence angles and mask angles are aligned. Thus, by usingthe probe 106 to provide feedback of the amount of ion beam currentdetected through the apertures 104, alignment of the mask 100 withrespect to the divergent angles of beam 103 as it travels through themask can optimize the available ion beam current incident on an intendedsubstrate 100. Consequently, by maximizing the amount of beam currentincident on the intended substrate 100, throughput of the implanter maybe optimized. The angles of the ion beam 103 in FIGS. 6-7 areexaggerated for clarity.

In FIG. 6, the mask 104 is shown misaligned to the ion beam 103. In thisparticular instance, the peak beam angles are not centered on themidpoint of the mask 104. Instead, the mean beam angle 600 of the ionbeam 103 is off-center with respect to the mask 104. To correct this,the mask 104 may be translated by a certain angle or distance to centerthe mean beam angle 600 to coincide with the center of the mask 104. Inanother instance, the beam 103 is adjusted to center the mean beam angle600 to coincide with the center of the mask 104. FIG. 7 is a second topcross-sectional view of mask-ion beam angular alignment. In thisembodiment, the mean beam angle 600 is coincides with the center of themask 104.

FIG. 8 is a first top cross-sectional view of mask-substrate alignment.FIG. 8 illustrates an ideal case where the ion beam 103 is aligned withthe mask 104 and the beam passes through the apertures 105 optimally.The resulting implant region matches the size (width in the x directionand length in the y direction) of the apertures 105. However, since theion beam 103 is composed of like-charged molecules or atoms as notedabove, the beam will diverge some small amount.

FIG. 9 is a second top cross-sectional view of mask-substrate alignment.FIG. 9 illustrates beam divergence. The ion beam 103 that passes throughthe apertures 105 does not have the same dimensions at the platen 102 asit did leaving the apertures 105. This divergence will vary based on theconditions of the ion beam 103. A small gap between the mask 104 andplaten 102 or substrate 100 on the platen 102 may minimize the effectsof beam divergence. Minimizing this gap between the mask 104 and platen102 or substrate 100 on the platen 102 may ensure that the actualimplant region will be similar to the desired implant region byminimizing the distance between the mask and the substrate within whichthe ion beam 103 has available to diverge. However, the gap between themask 104 and platen 102 or substrate 100 on the platen 102 may vary as aresult of machining tolerances, assembly tolerances, systems loads, orother reasons. Given the characteristic of the ion beam to diverge as ittravels, it is important to maintain as small a gap as possible in the Zdirection between the mask 104 and the substrate 100. If the gap is toolarge, then the implanted region will exceed the intended target regionon the substrate. In addition, the mask 104 may include alternativelyconfigured holes, slots, etc. (as mentioned above) that form a twodimensional pattern on the substrate 100. In this embodiment, the anglesin the X and Y direction determine the implant pattern fidelity.

To optimize the gap between the mask 104 and platen 102 or substrate 100on the platen 102, the Faraday probe 106 creates a feature profilemeasurement behind the mask 104. For example, FIG. 9A illustrates afeature profile where a large gap exists between the mask 104 and platen102 or substrate 100. As can be seen, a larger gap between the mask 104and platen 102 or substrate 100 on the platen 102 will cause theresulting profile to the Faraday probe 106 to be wider in dimension andshorter in peak amplitude. In one embodiment, the gap between the mask104 and platen 102 or substrate 100 on the platen 102 can be adjusted byservo motors, and then the Faraday probe 106 can confirm the profilesare within the specification for the substrate 100.

Over time, an ion beam 103 will erode the material of the mask 104 andin particular the edges of the apertures 105. This erosion is caused atleast in part by surface sputtering and thermal cycling. Eventually themask 104 will need to be replaced because the apertures 105 have erodedpast a specific tolerance or have incorrect dimensions. A Faraday probe106 can scan behind the mask 104 to monitor for this erosion. In oneinstance, an eroded mask 104 will exhibit a signal profile that has ahigh amplitude and large line width. FIG. 9B illustrates a signalprofile for a mask having worn apertures 105 (shaded region 105 a)overlayed on a signal profile for a mask having non-worn apertures(illustrated by middle portions 105 b). In particular, the currentsignal profile of the shaded regions shows a signal having a higheramplitude and larger line width than the signal associated with a maskhaving non-worn apertures. Since the height of the ion beam 103 canvary, the erosion of the mask 104 may not be uniform from one side ofthe aperture 105 to the opposite side of the aperture 105. In oneparticular embodiment, the Faraday probe 106 is positioned at an anglewith respect to the mask 104.

FIG. 10 is a front perspective view of an embodiment of a Faraday probeto test for mask erosion. Because the Faraday probe 106 is at an anglewith respect to the mask 104, the Faraday probe 106 is only exposed to aportion of the aperture 105 as it scans. FIGS. 11-13 are frontperspective views of the embodiment of a Faraday probe to test for maskerosion of FIG. 10 during translation of the Faraday probe. A profilefor the mask 104 will indicate if the dimensions of the apertures 105are not uniform.

In addition to erosion, the ion beam 103 may induce deposition orcoating of the mask 104. In this case, rather than the apertures 105growing in dimension, the apertures 105 will shrink or narrow indimension. As with erosion, this shrinking or narrowing of the apertures105 may vary from one side of the aperture 105 to the other side of theaperture 105 as well as along the length of the aperture. A Faradayprobe 106 can scan behind the mask 104 to monitor for coating. In oneinstance, a coated mask 104 with narrowed or shrunken apertures 105 willexhibit a signal profile that has a low amplitude and small line widthas compared to that shown in FIG. 9B.

The mask 104 may be composed of mechanically delicate materials orfeatures. Thus, fracturing of the mask 104 is a concern. This fracturingmay be caused by, for example, thermal loads, vibration, or erosion. Ifthe mask 104 fractures, the Faraday probe 106 will detect the missingportion of the probe. The broken or missing portion of the mask 104 willbe evident from the signal displaying ion beam 103 current in anunexpected area. Should this happen, in one embodiment, the Faradayprobe 106 indicates to the system that a fatal error has occurred andthat repair is required. Furthermore, by detecting such a fractured maskimproper implantation is prevented.

The mask 104 is exposed to strikes by the ion beam 103 during itslifetime. The amount of power dropped into the mask 104 depends on theparameters of the ion beam 103, such as total voltage or beam current.This power dropped into the mask 104 will create a thermal load on themask 104. The resulting thermal expansion of the material that the mask104 is composed of may cause positioning errors of the mask 104 or theapertures 105. Since this material in the mask 104 expands at a rateproportional to the thermal excursion of the mask 104, the Faraday probe106 can estimate the temperature of the mask 104 to ensure the mask 104stays within any functional limits. The pitch of the signal will varywith the temperature of the mask 104. Thus, as the apertures 105 changessize or dimensions due to thermal load, the Faraday probe 106 canmeasure these changes.

While the embodiments above use a Faraday probe 106, other measurementsystems, such as an optical digital imaging system, may be used alone orin conjunction with the Faraday probe 106. In this particularembodiment, the substrate 100 is examined after implantation. Theresulting image is captured and processed. The implanted regions on thesubstrate 100 will demonstrate the same signal variation as describedabove for each of the conditions or tests performed by the Faraday probe106. In another embodiment the mask 104 may be examined by opticalimaging and the resulting image captured and processed. The features onthe mask 104 should demonstrate the same signal variation as describedabove for each of the conditions or tests performed by the Faraday probe106. Periodic inspection of the mask 104 should match the results of theFaraday probe 106.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. A method for determining the condition of a maskused in an ion implanter comprising: directing an ion beam through aplurality of apertures of a mask toward a platen configured to support atarget substrate; translating an ion current measurement device betweensaid mask and said platen parallel to a location of said targetsubstrate during implantation; detecting an ion beam current incident onsaid ion current measurement device during said translating, whereinsaid ion beam current is associated with each of said apertures;generating a current signal in response to said ion beam current at aplurality of positions behind said mask; creating a current profile foreach of said apertures based on said current signal at said plurality ofpositions; and determining a dimension of each of said apertures basedon said current profile.
 2. The method of claim 1 further comprisingdetermining if one of said apertures has exceeded a threshold for saiddimension.
 3. The method of claim 1 further comprising determining ifone of said apertures is less than a threshold for said dimension. 4.The method of claim 1 further comprising determining if said mask hasfractured based on said determining said dimension.
 5. The method ofclaim 1, wherein said dimension is a width of said aperture.
 6. Themethod of claim 1, wherein said ion current measurement device isparallel to a length of said apertures.
 7. The method of claim 1,further comprising determining a temperature of said mask based on saiddimension.
 8. The method of claim 1, wherein said ion currentmeasurement device is at an angle with respect to said apertures.
 9. Amethod for determining the condition of a mask used in an ion implantercomprising: directing an ion beam through a plurality of apertures of amask toward a platen configured to support a target substrate, said maskbeing positioned orthogonally with respect to said ion beam, each ofsaid apertures having a dimension; disposing an ion current measurementdevice behind said mask co-planarly with respect to said targetsubstrate as if said target substrate was positioned on said platen andorthogonal with respect to said ion beam; translating said ion currentmeasurement device across said ion beam; detecting an ion beam currentincident on said ion current measurement device through said aperturesat a plurality of positions as said ion current measurement devicetranslates across said ion beam such that said ion beam current isassociated with said dimension of each of said apertures; generating acurrent signal in response to said ion beam current from said ioncurrent measurement device at each of said positions; creating a currentprofile for each of said apertures based on said current signal as saidion current measurement device translates across said ion beam; anddetermining said dimension of each of said apertures.
 10. The method ofclaim 9 further comprising changing an angle of said ion currentmeasurement device with respect to said apertures of said mask.
 11. Themethod of claim 9 further comprising determining if one of saidapertures has exceeded a threshold for said dimension.
 12. The method ofclaim 9 further comprising determining if one of said apertures is lessthan a threshold for said dimension.
 13. The method of claim 9, whereinsaid dimension is a width of said aperture.
 14. The method of claim 9,wherein said ion current measurement device is parallel to a length ofsaid apertures.
 15. The method of claim 9, further comprisingdetermining a temperature of said mask based on said dimension.
 16. Themethod of claim 9, wherein said ion current measurement device is at anangle with respect to said apertures.